.container {
  width: 200px;
  height: 200px;
  position: absolute;

  background: linear-gradient(#03a9f4, #03a9f4),
    linear-gradient(90deg, #ffffff33 1px, transparent 0, transparent 19px),
    linear-gradient(#ffffff33 1px, transparent 0, transparent 19px),
    linear-gradient(transparent, #2196f3);
  background-size: 100% 1.5%, 10% 100%, 100% 10%, 100% 100%;
  background-repeat: no-repeat, repeat, repeat, repeat;

  background-position: 0 0, 0 0, 0 0, 0 0;
  clip-path: polygon(0% 0%, 100% 0%, 100% 1.5%, 0% 1.5%);

  animation: move 2s linear infinite;
}

@keyframes move {
  to {
    background-position: 0 100%, 0 0, 0 0, 0 0;
    clip-path: polygon(0% 0%, 100% 0%, 100% 100%, 0% 100%);
  }
}
